Hi John. Welcome to the forum.
I am no expert but I will share what little I know plus offer my opinion. Generally, bits with 1/4" shanks are used for hand held routing and the 1/2" shanks are used in router tables. So much depends on whether you will be taking your router to your work or taking your work to the router table. Generally, for sign making you would use a smaller lighter weight router with a 1/4" collet. Only you can make your best prediction.
As for me, I decided to buy some sets of router bits. Many will suggest that you buy only the bits you need. I take the more expensive shotgun approach and have available to me a wider variety of bits to try thus giving me more experience with a variety of bits. I purchase medium priced sets to gain this experience. Then as I use the bits, I see which ones I use the most and then I will purchase the more expensive bit of that model. This is how I build my collection. Everyone has their own style. You will choose your personal style also as you start out.
Now, for medium (not cheap) router bits I have purchased the Yonico brand (among others). You can start out with whatever size set you feel comfortable with. Look at the profiles and consider their use before you buy. For example, they sell a 50 bit set for $115. Type in the coupon “5off” and get $5 off at checkout. Here is their website: Router Bit Sets :: Large Sets :: 50 Bits Professional Quality Router Bit Set C3 Carbide 1/2" Shank Yonico 17502
They are a relatively young manufacturer and I decided to take a chance with them. Reviews are mixed but it serves my purpose.
Now, when replacing them or right from the start however you decide, some excellent router bit manufacturers are Whiteside, Amana, Freud and Eagle America. I also own bits from each of those manufacturers and they are all excellent but a bit more pricey.
Stay away from cheap bits, Harbor Freight. Woodworkers spend booga bucks on table saws, routers, router tables, etc. but then skimp on where the metal (carbide) meets the wood. Buy quality saw blades and router bits. Sharp bits will provide satisfying results while mediocre blades and bits will not. They also present safety issues.
So John, like each of us starting out, you must make some decisions on how you want to approach this, namely buy what you need when you need it or buy into sets to increase your exposure to a wider variety of bits in less time. Then when you do buy the more expensive quality bits, you will know why and be able to do so with confidence. You also will not be spending money on expensive bits that you will rarely use.
Do not buy cheap. For your long term quality bits, stick with Whiteside, Amana, Freud and Eagle America. Many folks like Bosch, CMT, MCLS, Rockler and others.
Customer service means a lot also.
Hope this helps.